Stabilized mineral oil composition



Patented Aug. 10, 1943 2,326,483 STABIIJZED MINERAL OIL COMPOSITION Robert 0. Moran, Wenonah, N. 1., as'signor to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York No Drawing; Application July 2.0, 1940,

Serial No. 346,655 I 11- Claims.

This invention is concerned with the stabilization of viscous mineral oil fractions against the harmful effects of oxidation or deterioration with use by means of antioxidants or oxidation inhibitors added to the oil. The invention is more specifically related to the improvement or stabilization of such mineral oil fractions by the use of novel compounds, or a novel class of compounds. which when admixed with a viscous mineral oil in minor proportions will prevent or delay undesirable changes taking place in the oil.

As is well known to those familiar with the art, substantially all the various fractions obtained from mineral oils and refined for their various uses are susceptible to oxidation. The susceptibility of an oil fraction to oxidation and the manner in which oxidation manifests itself within the oil varies with the type and degree of refinement to which the oil has been subjected and with the conditions under which it is used or tested. In other words, the products formed in an oil fraction as a result ofioxidation and the degree to which they are formed depends upon the extent to which the various unstable constituents or constituents which may act as oxidation catalysts have been removed by refining operations, and also upon the conditions of use.

A highly refined viscous oil, for example, which is normally an oil that has been refined by treatment with fuming sulfuric acid or other means or combinations such as AlCla, solvents and acids with large quantities of concentrated sulfuric acid), tends to form relatively large amounts of acidic constituents when subjected to oxidizing conditions. The presence of catalytic materials such as copper does not appear to affect appreciably the oxidation of highly J refined oils, and such oils are less prone to the formation of colored bodies or of insoluble sludge. The formation of acidic bodies, however, is highly undesirable for most applications of these oils. For example. when used as an insulating or cooling oil in electrical equipment such as transformers or capacitors an increase in acidic bodies tends to lower the dielectric strength of the oil and has other harmful effects which are undesirable. The acids are corrosive to metals and thus reduce the useful life of the oils as lubricants or for other purposes in which they come in contact with metals, and the acidic materials are also iniurious in textile lubricants and in spray oils.

-Moderately refined oils, that is, oils that have been refined by treatment with only moderate amounts of sulfuric acid, or other refining agents, tend to form relatively small amounts of acidic oxidation products as compared with highly refined oils, but they undergo material color depreciation and form considerable amounts of sludge. The changes taking place in these oils are appreciably accelerated by the presence of metal catalysts such as copper. Suflicient acid is generally formed to cause some reduction in the dielectric strength of these oils, b the principal objection to them is their tende cy to deposit sludge which interferes with heat transfer in transformers and turbines and also causes plugging of oil feed lines in lubricating systems.

Solvent-refined oils, in general, which have been prepared by treatment with selective solvents, such as chlorex, 'plienol, furfural, etc., resemble the moderately refined acid-treated oils in that their oxidation is accelerated by the presence of metalssuch, as copper and further in that it is attended by substantial color depreciation and sludge formation. Acid formation is usually greater than in the case of moderately acidrefined oils, but considerably less than with hig y refined oils; Both sludge and acid formation lower their value for many purposes, such aselectrical insulation, lubrication, etc. Also, solvent-refined oils have found extensive use aslubricants for internal combustion engines because of their high viscosity index, but under the conditions of use encountered in crankcases such oils develop constituents which are corrosive toward certain metal bearings such as the cadmium-silver bearing, etc., which are sometimes used.

' It is to be understood that this classification of required toproduc'e these types of oils varies with the crude source so that any one refining pro--' cedure may produce either a highly refined oil or a moderately refined oil, depending uponv the crude source. Pennsylvania type oils, for example, require much less refining to produce highly refined cilsthan the Coastal tym of oils,

The use of oxidation inhibitors for the purpose of stabilizing a viscous mineral oil fraction against the deleterious effects of oxidation discussed above is well known. Since the action of these inhibiting materials is apparently cata-i lytic, the problem of their development is a difficult one and is evidently influenced to a large degree by the oxidizable constituents which are in the oil following a particular refining treatment. Thus, a particular inhibitor or class of inhibitors may be effective to stabilize a highly refined oil against acid formation while the same inhibitor may have no appreciable effect upon acid, color or sludge formation in a moderately refinedoil and vice versa. This same inhibitor may or may not be effectivein inhibiting acid,

sludge and color formation in a solvent-refined oil and may or may not be effective to inhibit the corrosive action of a solvent-refined oil toward metals such as used in cadmium-silver bearings.

One of the principal features of the compounds or class of compounds contemplated herein resides in their property of acting as negative catalysts toward the oxidation of highly refined oils, solvent-refined oils and moderately refined oils.

In my copending application Serial No. 254,689, filed February 4, 1939 (now Patent No. 2,220,941) of which the present application is a continuation in part, I have disclosed for mineral oils a class of compounds obtained by the reaction of an alkali metal mercaptide with beta-beta dichlor diethyl ether. Those compounds, which were broadly classified as dimercaptyl diethyl ethers, have the general formula in which R represents a hydrocarbon radical such as an alkyl or aryl group. It will be observed that the compounds of the aforesaid former application are characterized by the presence of a diethyl ether group interposed between two RS. groups.

I have now discovered that the general class of compounds herein identified 'as the dimercaptyl alkyl ethers, are effective antioxidants for viscous mineral oils of the type discussed hereinabove. The general class of compounds contemplated herein, of which the aforesaid di- =mercaptyl diethyl ether is a member, are typified by the general formula RS-Z-SR, in which R represents a hydrocarbon radical selected from the group consisting of alkyl, aryl, aralkyl, and alkaryl and Z represents a monoor poly-alkyl ether. Stated in another way, Z represents an alkyl ether group having at least one ether linkage.

Typical compounds satisfying the foregoing general formula in which Z represents a monoether group are represented by the formula in which the R's represent aliphatic hydrocarbon groups. Compounds in which Z is a polyether group-that is, an ether group having more than one ether linkage-are typified by the formulae in which the R's represent alkyl groups and R is as defined above. Specific examples of the latter type of compounds are the dimercaptyl triglycols and the dimercaptyi tetraglycols having the respective formulae:

and

As aforesaid, a typical procedure for synthesizing compounds of the type contemplated herein is to react an alkaline solution of a mercaptan or thiophenol (alkali mercaptides) with the dichlor, ether compound. The reaction may be represented by the following equation:

in which X represents an alkali metal. These compounds may be broadly referred to as dimercaptyl alkyl ether compounds, specific preferred and the mixture refluxed for several hours.

classes within the general group being the dialkyl mercaptyl alkyl ethers and the diaryl mercaptyl alkyl ethers.

Typical procedures whereby the compounds contemplated herein may be prepared are illustrated by the following examples:

EXAMPLE ONE 1 PREPARATION OF DIAMYLMERCAPTYL DI-ISOPROPYL Errma Twenty-eight grams of KOH (.5 mole) and 52 grams of amylmercaptan (.5 mole) were dissolved in 500 cc. of ethyl alcohol and the solution heated to reflux temperature. Forty-four grams of dichlor-isopropyl ether (.25 mole) were added and the refluxing continued for 4 hours. The mixture was poured into water, and the oil separating was taken up in benzol, washed with water, and the benzol layer was then dried over CaClz. The solvent was distilled off and the remaining oil was then vacuum-distilled at 3 mm. pressure. A yellow oil was obtained that boiled between 141 and 158 C. at 3 mm.

EXAMPLE TWO PREPARATION OF DIPHENYLMERCAPTYL DI-ISOPROPYL ETHER' Eleven grams of thiophenol (1 mole) and 5.6 grams of KOH (.1 mole) were-dissolved in cc. of ethyl alcohol. The solution was heated to reflux temperature and 8.5 grams of dichlor-isopropyl ether (0.5 mole) were added. After 4 hours refluxing, the mixture was treated as described above. The resulting oil was heated to 200 C. at 3 mm. pressure to remove unreacted material, and this left a reddish brown oil as a residue.

EXAMPLE THREE P'RaPARA'rIoN OF DIAMYLMERCAPTYL TETRAGLYCOL Twenty-eight grams of KQH (.5 mole) and 52 grams of amylmercaptan (.5 mole) were dissolved in 200 cc. of ethyl alcohol, and the solution was heated to reflux temperature. Fifty-eight grams of tetraglycol dichloride (.25 mole) were added The product was poured into water, extracted with benzol, water-washed, and then dried. On evaporation of the solvent 2. yellow oil was obtained, most of which boiled at -204 C. at 4 mm. pressure.

The procedures to be followed in preparing other typical compounds falling into the general class contemplated herein will be obvious from the foregoing examples. As aforesaid, my invention contemplates the general class of alkyl-mercaptans and thiophenols for obtaining the RS-- group in the general formula. tion contemplates the general class of dichlor alkyl ether compounds containing one or more ether linkages, for obtaining the Z group of the general formula according to the procedures outlined above. It is also to be understood that the present invention contemplates the use of the general class of mercaptyl alkyl ethers as antioxidants for viscous mineral oil compositions irrespective of the procedurefollowed in preparing such compounds.

The effectiveness of the compounds contem plated herein as antioxidants for viscous mineral oil fractions is shown by the following examples.

EXAMPLE A (OILS HIGHLY REFINED BY SULFURIC AcIn) A highly refined oil, suitable for use in transformers, had been prepared by treating a Coastal Also, my invendistillate with 40 pounds of 98 percent sulfuric acid and 180 pounds of 103 per cent oleum per barrel, followed by washing and clay percolation. The finished oil had a specific gravity of 0.871, a flash point of 310 F., and a Saybolt Universal Viscosity of 69 seconds at 100 F. It was tested by heating samples to a temperature of 120 C. and bubbling oxygen through them for '70 hours. The acids thus formed were determined by titrating with alcoholic KOH, the results being recorded as neutralization numbers (N. N.) which represent the number of milligrams of KOH re: quired to neutralize the acids iormed in one gram of oil. Results for the oil alone and oil blends containing typical dimeicaptyl alkyl ether compounds of the type contemplated herein are set forth in Table I below.

Table I ssssssss 9999. 9???- assesses? EXAMPLE B (OILS Monana'rsny Barman WITH Soarmuc item) A mixed Mid-Continent and Coastal distillate had been refined by treatment with 70 pounds of 98 per cent sulfuric acid per barrel, neutralized, washed and percolated through clay. The finished oil had a, specific gravity of 0.879, a, flash point of 385 F'., and a Saybolt Universal Viscosity of 152 seconds at 100 F. It was an oil suitable for use in turbines. The test employed was as follows: 25 cc. samples of the oil were maintained at a, temperature of 200 F. with liters of air per hour bubbling therethrough. Each sample contained 24 inches of #18 gauge copper wire and 1 gram of iron granules, and 2 cc. of distilled water were added each day. The sample were tested for acidity, color and sludge after varying periods of time. The results obtained are given in Table II below:

Table II Sludge mg./25 cc.

Per cent Time, hours Oil alone Diamylmercaptyl dimethylether Diphenylmercaptyl dimethylether Diamylmercaptyl diisopropylether.- l0

Diphenylmercaptyl diisopropylether- Diamylmercaptyl triglycol Diphenylmercaptyl mglycol Diamylmercaptyl tetraglycol Diphenylmercaptyl tetrnglycol (Ons Barman BY Means or SOLVENTS) In this test the oil used was a distillate from a Rodessa crude'which had been solvent-refined with furfural, dewaxed and filtered. The fluished stock had a specific gravity of 0.856, a flash point of 420 F., and a Saybolt viscosity .of 151 sec. at F. The oil was tested by the same -procedure described in Example 0 above. The

results obtained are listed in Table 111.

Table 1']! Per Time, Lav. Sludge cant hours color mg./25 cc.

01181011 02 .91 9 33 20.3 320 -251 Diamylmercaptyl dlmethylether 10 166 28. 7 235 148 Diphenylmermptyl di-' methylether-.. .10 167 6.2 120 g 79 191 11.0 190 Diamylmercaptyl diimpropylether.-. 10 167 13. 0 70 m Diphenylmeroaptyl diisopropylether..---..-. 10 167 0. 8 75 91 191 15. 1 130 179 Diamylmercaptyl triyoo .10 167 14.8 82 46 Di henylmercaptyl trie g ycol 10 166 28. 4 335 197 Diamylmercaptyl tetraglgco .10 143 18.7 270 329 D p enylme'rcaptyl tetraglycol .10 148 19.8 240 236 EXAMPLE D '(Conaosrorz Tnsr) of the compounds contemplated herein as inhibitors of such corrosive action in a solvent-refined oil the following test was used:

A section of a bearing containing a cadmiumsilver alloy surface and weighing about 6.0 grams was placed in 30 grams of the motor oil sample to be tested. The oil was heated to C. for 22 hours while a stream of air was bubbled against the surface of the metal specimen. The

loss in weight of the bearing during this treatment is an indication of the extent to which corrosion has taken place. The oil used in this test was a motor oil (S. A. E. 20) obtained fror'n-- a mixture of' Pennsylvania neutral and residuum stocks solvent-refined by extraction with chlorex';

it had'a specific gravity of 0.872, a flash point of 435 F.,'and a Saybolt viscosity of 318 seconds at 100 F.

The results listed in Table IV below were obtained with the oil just described above when tested alone and'with the addition of typical dimercaptyl alkyl ethers. In each case a sample ples above.

It will be observed from the foregoing results that the dimercaptyl alkyl ethers as a generic class possess the property of inhibiting the deleterious efiects of oxidation in mineral oil fractions of the highly refined, moderately refined, and solvent-refined types. In this regard it is to be understood that the terms highly refined, moderately refined, and "solvent-refined as used herein are not necessarily confined to oils obtained by specific methods of refining but are intended as indicative of oils having deterioration characteristics and inhibitor response similar to the illustrative oils given in the exam- In this same regard, it is again pointed out that the crude stock from which the oil is obtained, as well as the refining treatment, is a factor efl'ecting its characteristics. It is possible, for example, by selection of the crude stock to obtain an oil having highly refined characteristics with a treatment that would Yield a moderately refined oil from another crude stock.

The amount of the compound used may be varied depending upon the type of oil fraction with which it is blended and the conditions under which it is used. In general it appears that the compounds contemplated herein can be used in amounts ranging from 0.01 per cent to 1.00 per cent with amounts ranging from 0.05 per cent to 0.50 per cent giving satisfactory results.

I claim:

1. An improved mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion of a dimercaptyl alkyl ether in an amount sufiicient to inhibit the deleterious effects of oxidation on the oil.

2. An improved mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion of a dialkylmercaptyl alkyl ether in an amount suflicient to inhibit the deleterious effects of oxidation on the oil.

3. An improved mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion of a diarylmercaptyl alkyl ether in an amount sufficient to inhibit the deleterious effects of oxidation on the oil.

4. An improved mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion of a compound having the general formula in which the R represents a hydrocarbon radical and Z represents an alkyl ether group having at least one ether linkage, said compound being present in an amount suflicient to inhibit the deleterious eflects of oxidation in the oil.

5. An improved mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion of a compound having the general formula in which R represents a hydrocarbon radical and the Rs represent alkyl radicals, said compounds being present in an amount suflicient to inhibit the deleterious efiects of oxidation in the oil.

6. Animproved mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion of a compound having the general formula in which R represents a hydrocarbon radical and the Rs represent alkyl radicals, said compound being present in an amount sufficient; to inhibit the deleterious effects of oxidation in the oil.

7. An improved mineral oil composition com prising a viscous mineral oil fraction having in admixture therewith a minor proportion of a compound having the general formula RSR'--OR- OR'-ORSR in which R represents a hydrocarbon radical and the R's represent alkyl radicals, vsaid compound being present in an amount sufiicient to inhibit the deleterious effects of oxidation in the oil.

8. An improved mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith aminor proportion of a compound selected from the group consisting of: diamylmercaptyl dimethylether; diphenylmercaptyl dimethylether; diamylmercaptyl, di-isopropylether; diphenylmercaptyl di-isopropylether; diamylmercaptyl triglycol; diphenylmercaptyl triglycol; diamylmercaptyl tetraglycol;

and diphenylmercaptyl tetraglycol, said comcaptyl triglycol; diamylmercaptyl tetraglycol;

and diphenylmercaptyl tetraglycol, said compound being present in an amount ranging from about 0.1 per cent to about 1.0 per cent.

10. An improved mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith from about 0.1 per cent to about 1.0 per cent of a compound having the general formula RS--ZSR in which the Rs represent hydrocarbon radicals and Z is an alkyl ether group having at least one ether linkage.

11. An improved mineral oil composition comprising a viscous mineral oil fraction having in admixture therewith a minor proportion of diamyl mercaptyl dimethyl ether in an amount sufficient to inhibit the deleterious effects of oxidation in the oil.

ROBERT C. MORAN.

CERTIFICATE OF comcrmn Patent no. 2,326,h83. August 10, 1915.

ROBERT C. MORAN.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, ,line 28, Example 2, for "(1 mole)" read --(.1 mole)--; pagph, second column, lines 10, 20 and 29, for "R read --R s--; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this lLLth day of September, A. D. 1911.5.

Henry Van Arsdale, (seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION? Patent No. 2,526,l|.85. August 10, 1915.

ROBERT C. MORAN.

It is hereby certified that error appears in the printed specification of the shore numbered patent requiring correction as follows: Page 2, sec- 0nd column, line 28, Example 2, for "(1 mole)" read --(.1 mole)--; pageh, second column, lines 10, 20 and 29, for "'R read -R s-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11 th day of September, A. D. 1915.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents. 

